The importance of using multiple antennas in multiple input multiple output systems (MIMO) has been well understood. However, much focus has been on using vertically polarized spatial antenna array configurations.
Although spatial MIMO configurations have proven to be quite effective, a number of problems still exist with such spatial configurations. Most cellular propagation scenarios are characterized by the existence of a strong dominant path causing the spatial MIMO channel matrix to be rank deficient. Furthermore, an inter element spacing requirement in spatial configurations restricts the amount of permissible scaling down of a mobile device, as one attempts to make a mobile device more and more compact. Also, the interference resulting due to spatial antenna arrays is much higher as compared with the interference between a vertically polarized antenna and a horizontally polarized antenna. Thus, for one or more of the above reasons, there can be advantages in implementing an approach of using differently polarized antennas over an approach of using spatial antenna array with a single polarized antenna direction.
In view of the above discussion, it would be desirable if improved methods and apparatus could be developed to improve user experience in propagation scenarios characterized by a strong dominant path, without compromising compactness and size of mobile devices and without adding too much complexity to the current system in use.